Date: Mon, 23 Dec 1996 13:59:06 GMT From: hans@brandinnovators.com (Hans Zuidam) To: FreeBSD-gnats-submit@freebsd.org Subject: kern/2271: FIONREAD in if_tun.c wrong Message-ID: <199612231359.NAA01354@truk.brandinnovators.com> Resent-Message-ID: <199612231320.FAA03658@freefall.freebsd.org>
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>Number: 2271
>Category: kern
>Synopsis: FIONREAD on tunnel device returns incorrect value.
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Dec 23 05:20:01 PST 1996
>Last-Modified:
>Originator: Hans Zuidam
>Organization:
Brand Innovators B.V.
>Release: FreeBSD 2.1.5-RELEASE i386
>Environment:
tunnel device configured
>Description:
When doing a FIONREAD ioctl on the tunnel device, it returns
the value of m_len, while it should return the value of
m_pkthdr.len (if M_PKTHDR is set.)
>How-To-Repeat:
Using a propriatary TCP/IP stack it was discovered that large TCP
packets would not be read correctly. The FIONREAD would report
that there were 40 bytes in the packet, while there were actually
many more.
Note: none of the programs supplied with FreeBSD that use the tunnel
device, use FIONREAD. All request as much as possible from a read.
>Fix:
Workaround by doing MAXINT reads (or something similar...) on a
/dev/tun. Below is a patch which is believed to be correct.
*** sys.org/net/if_tun.c Fri Dec 20 15:20:00 1996
--- sys/net/if_tun.c Mon Dec 23 09:51:22 1996
***************
*** 418,425 ****
break;
case FIONREAD:
s = splimp();
! if (tp->tun_if.if_snd.ifq_head)
! *(int *)data = tp->tun_if.if_snd.ifq_head->m_len;
else
*(int *)data = 0;
splx(s);
--- 418,429 ----
break;
case FIONREAD:
s = splimp();
! if (tp->tun_if.if_snd.ifq_head) {
! if (tp->tun_if.if_snd.ifq_head->m_flags & M_PKTHDR)
! *(int *)data = tp->tun_if.if_snd.ifq_head->m_pkthdr.len;
! else
! *(int *)data = tp->tun_if.if_snd.ifq_head->m_len;
! }
else
*(int *)data = 0;
splx(s);
>Audit-Trail:
>Unformatted:
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